The European Union stepped up its criticism of investigation and detention of Turkish academics who signed a declaration that criticized government policies in the Southeast, calling on Turkey to uphold freedom of expression.

"The steps taken against the Turkish academics who signed a declaration regarding events in the Southeast of Turkey are an extremely worrying development," the EU said in a statement on Saturday.

Prosecutors have launched an investigation against more than 1,000 academics who signed the statement that criticize curfews and military operations in the predominantly Kurdish southeastern districts, soon after President Recep Tayyip Erdo?an accused the signatories of "treachery." More than 20 of them were detained, and later released, on Friday.

Scores of them also face administrative investigations while some have been suspended from their university posts.

"While reaffirming our strongest condemnation of all forms of terrorist attacks, including by the PKK, and the attack on the police headquarters in Ç?nar on 14 January, we restate that the fight against terrorism must fully respect obligations under international law, including human rights and humanitarian law," the EU statement said -- referring to a PKK attack that killed six people in Ç?nar district in Diyarbak?r, including a baby and two children.

President Erdo?an continued his criticism of the academics after detentions on Friday, calling them "despicable," "cruel" and claiming they are equally guilty of the PKK attacks including the one in Ç?nar because they support the terrorists.

"Freedom of expression must be upheld, in line with the Copenhagen political criteria; an intimidating climate goes against this. We expect Turkey ensures that its legislation is implemented in a manner which is in line with European standards enshrined in the European Convention for Human Rights and the case-law of the European Court of Human Rights," the EU said.

"The EU reiterates its strong belief that the Kurdish peace process remains the only way to solve a conflict that continues to claim far too many lives, and remains ready to support all efforts in this direction," said the EU.

The actions against the academics has caused an outcry both in Turkey and abroad. The US State Department said the developments were part of a "troubling trend in Turkey, whereby official bodies, law enforcement, and judicial authorities are being used to discourage legitimate political discourse" while the US ambassador in Ankara, John Bass, wrote in a statement that "expressions of concern about violence do not equal support for terrorism. Criticism of government does not equal treason."

British envoy expresses concern

British Ambassador to Turkey Richard Moore also joined the criticism on Saturday, saying in a statement that he was "very concerned to hear reports of academics being suspended and investigated for expressing their views on conflict in Southeast."

"Freedom of expression is vital in a democratic society, and especially in education. That includes the right to express views we might think are mistaken, or one-sided," Moore said.